When you look at the results of the polls in your own hubs they stay opened until you close the document. After you close the document and then reopen it, the poll should be just the way it was before you checked the results.
I've noticed that it is possible to view the results in polls in anyone's hub and if I do that there is usually a link that says "go back and vote," under the graph, meaning I can go back to the original form before I viewed the results.
My polls are working fine. I think you'll find that if you close your hub and then reopen it, the poll will be just as it was before you viewed the results.